Re: Parallel INSERT (INTO ... SELECT ...)

On Fri, Sep 25, 2020 at 2:31 PM Bharath Rupireddy
<bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
>
> On Tue, Sep 22, 2020 at 10:26 AM Greg Nancarrow <gregn4422(at)gmail(dot)com> wrote:
> >
> > For cases where it can't be allowed (e.g. INSERT into a table with
> > foreign keys, or INSERT INTO ... SELECT ... ON CONFLICT ... DO UPDATE
> > ...") it at least allows parallelism of the SELECT part.
> >
>
> Thanks Greg for the patch.
>
> 2. What happens if the target table has triggers(before statement,
> after statement, before row, after row) that are parallel unsafe?
>

In such a case, the parallel insert shouldn't be selected. However, we
should still be able to execute the Select part in parallel.

> 3. Will each worker be doing single row insertions or multi inserts?
> If single row insertions, will the buffer lock contentions be more?
>

I don't think the purpose of this patch is to change the basic flow of
how Insert works and also I am not sure if it is worth the effort as
well. I have answered this earlier in a bit more detailed way [1].

[1] - https://www.postgresql.org/message-id/CAA4eK1Ks8Sqs29VHPS6koNj5E9YQdkGCzgGsSrQMeUbQfe28yg%40mail.gmail.com

--
With Regards,
Amit Kapila.